Corrosion behavior of diverse sputtered coatings for the helium cooled pebbles bed (HCPB) breeder concept

Abstract

The present paper studies the corrosion behavior of several sputtered coatings (nanostructured W, SiC and Al2O3) under the working conditions expected for the helium cooled pebbles bed breeder concept to be used in future nuclear fusion reactors. To this purpose, coatings were evaluated during 240 h at a temperature of 550 ◦C in Helium atmosphere with 120 ppms of water to simulate the purge gas in the presence of ceramic pebbles whose composition was a mixture of lithium silicate/titanate. The 3-D topography, morphology, microstructure and elemental composition of the coatings were studied prior to and after the corrosion tests. Results evidence that coatings show quite different corrosion behavior: Because of oxidation, nW is completely ruled out for such application, the corrosion behavior of Al2O3 coating is questionable whereas, SiC coating is shown to act as a real corrosion barrier. Nanoscratch measurements of this last coating show that it also has a good adhesion to the Eurofer substrate both prior to and after the corrosion test.